The invention relates to a process for the production of a two-layer electrodeposition coating on three-dimensional electrically conductive objects.
The production of two-layer electrodeposition coatings is known in the prior art. For example, multi-layer coatings composed of a two-layer electrodeposition coating which is overcoated with a clear coat or a base coat/clear coat layer are known from U.S. Pat. Nos. 5,908,667 and 5,882,734.
In the conventional production of two-layer electrodeposition coatings, an electrodeposition coat primer layer is initially deposited from an electrodeposition coating agent containing electrically conductive constituents on a metal substrate. After the electrodeposition coating layer has been cured by stoving (baking), the latter is sufficiently electrically conductive for a second electrodeposition coating layer to be deposited on it electrophoretically from a second electrodeposition coating agent and likewise stoved (baked). Overcoating with further coating layers may then take place.
This invention further develops the coating process of the prior art for coating three-dimensional objects having surface regions that are visible and not visible to the observer and saves electrodeposition coating agent and simplifies the coating process.
The invention relates to a process for the production of a multi-layer coating in which a primer layer that is electrically conductive in the at least partially cured state is applied by electrodeposition from an electrodeposition coating agent (I) to an electrically conductive three-dimensional object, at least partially cured exclusively by the action of near infra-red radiation substantially only on the surfaces of the object exposed to the radiation, and an additional coating layer is applied by electrodeposition from an electrodeposition coating agent (II) that is different from electrodeposition coating agent (I), and then this additional coating layer as well as completely uncured or incompletely cured area parts of the primer layer produced from electrodeposition coating agent (I) are cured.